The present invention relates to an instrument for use in radiotherapy, and more particularly to an instrument for inserting hollow stainless steel needles into the body during the treatment of malignant tumors by interstitial implantation of radioactive materials.
The interstitial implantation of radioactive isotopes is a well established technique for the treatment of malignant tumors. Short lengths of a radioactive source, such as Iridium-192, are linearly arranged within thin walled plastic tubes to form "ribbons." These ribbons are used as temporary interstitial implants in a wide variety of clinical situations. Each ribbon, which is very flexible, must be inserted into the body with the aid of a rigid trocar, in the form of a hollow stainless steel needle, which is sharpened at one end for piercing the skin and tumor bearing tissue. An array of the hollow needles are first inserted into the tissues to be implanted. The needles are typically spaced evenly throughout the volume of tissue to be irradiated, and are parallel to one another to avoid areas of underdose or overdose. After the hollow needles have been inserted, ribbons of radioactive sources are inserted into the bores of the needles to a position determined by the location of the tumor bearing tissue. In certain clinical situations the needles may be left in place in the body, along with the sources, for the duration of the implant, after which both are removed. In other situations, the needles may be pulled out of the body, leaving behind only the ribbon sources for the duration of the implant.
In the prior art, each needle was inserted into the body with the aid of a pin-vise which gripped the needle in a collapsible collet. This was done for several reasons. First, the needles are of a small diameter, typically 17 gauge (1.5 mm), and are very difficult to grip by hand. Second, the force needed to push even a sharp needle through the skin and connective tissue is considerable, necessitating a grip on the needle that is greater than can be obtained with the hand alone. Third, the needle must be gripped close to the point of entry into the body to avoid bending, due to its small diameter, especially when long needles, of up to 25 cms. are to be inserted. In using the standard pin-vise to grip the needle, the collet is compressed by screwing the binding nut tight with one hand while holding the handle of the pin-vise stationary with the other hand. Two hands are therefore needed to screw and unscrew the binding nut of the pin-vise in order to secure and release the collet from the needle. To fully insert an implant needle of typical length by such means, requires the repeated repositioning of the vise back along the needle as the needle is progressively pushed deeper into the body. The radiotherapist is required to alternately shift one hand from its position steadying the patient's body and feeling for the point of the needle as it approaches the intended area of the implant, to its positions for securing and releasing the pin-vise. This is awkward, time consuming, and becomes more difficult when several needles have already been inserted, leaving little room close to the needle entry area for the hands to fit in order to screw and unscrew the binding nut, especially when working deep within the body. The prior art method, which requires the removal and repositioning of the radiotherapist's hand from its position steadying the patient after each adjustment of the pin-vise, also interrupts the bimanual stereotactic guiding of the point of the needle as it passes through the tissue. A device for inserting an implant needle that does not require two hands to manually secure and release a collet by turning a threaded binding nut therefore would be of great advantage in permitting faster, easier, and smoother insertion of the needles.